Hacker Barnaby Jack, perhaps best known for discovering insecurities in pacemakers that could be exploited with fatal results, has died in San Francisco, Reuters reports. He was 35. His death comes just a week before he was scheduled to present more information on his pacemaker hack at an information security conference. Reuters did not have any details about the cause of death.

Jack was last employed by the cyber security consulting firm IOActive Inc, and specialized in embeddable devices (like the computers one finds in ATMs or medical devices). Jack worked as a white-hat hacker, looking for flaws in systems so that they could be fixed. One of his earlier exploits was finding a flaw in insulin pumps that made it possible for someone to remotely deliver fatal doses of insulin. He also, famously, found a vulnerability in ATMs that made them spit out money, as seen in the video above. By figuring out how to exploit these systems, Jack provided information that companies needed to make their products more secure.

Read more about his pacemaker hack here.